Reply To: Shaders: How to enabled it? And where? (Retropie virgin inside)

[Floob]

This video is a little dated, but it should give you the gist

Basically you set your shader in the file (for each system)
/opt/retropie/configs/{systemname}/retroarch.cfg

https://www.youtube.com/watch?v=owsdsyIDU6A&ab_channel=Floob